Because LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered by many to have the potential to completely replace cathode ray tube (CRT) monitors and televisions.
FIG. 3 is a schematic, exploded side view of a conventional LCD device. The LCD device 1 includes a liquid crystal (LC) panel 11, and a backlight module 12 arranged under the LC panel 11. The backlight module 12 provides light beams to the LC panel 11 so that the LC panel 11 is able to display images.
The LC panel 11 includes a top substrate 191, a bottom substrate 192 parallel to the top substrate 191, and a liquid crystal layer 190 sandwiched between the top substrate 191 and the bottom substrate 192.
The backlight module 12 includes an optical film unit 13, a light guide plate (LGP) 15, a reflective plate 17, and a light source 16. The LGP 15 includes a light incident surface 151, a top light emitting surface 152 adjoining the light incident surface 151, and a bottom surface 153 adjoining the light incident surface 151. The light source 16 is a set of light emitting diodes (LEDs), and is disposed adjacent to the light incident surface 151 of the LGP 15. The optical film unit 13 is disposed adjacent to the light emitting surface 152. The reflective plate 17 is disposed adjacent to the bottom surface 153.
Light beams emitted by the light source 16 enter the LGP 15 through the light incident surface 151. Most of the light beams are reflected by the bottom surface 153 of the LGP 16, and then transmit through the light emitting surface 152. Some of the light beams transmit out of the LGP 15 through the bottom surface 153, are reflected by the reflective plate 17 back into the LGP 15, and then transmit through the light emitting surface 152. The light beams emitting from the light emitting surface 152 transmit through the optical film unit 13 to illuminate the LC panel 11.
When the light beams illuminate the LC panel 11, simultaneously, an electric field is applied between the top substrate 191 and the bottom substrate 192. Liquid crystal molecules of the liquid crystal of the liquid crystal layer 190 are driven by the electric field to rotate from one direction to another direction. The liquid crystal molecules work as light switches, and allow certain parts of the light beams to pass through the LC panel 11. Thereby, the LC panel 11 displays images.
The freezing point of the liquid crystal is about −40° C. When the temperature of the liquid crystal is in the range from −10° C. to −30° C., the liquid crystal layer 190 becomes stickier, and the liquid crystal molecules rotate slower than normal. This is liable to cause flicker and image delay. That is, the display quality of the LCD device 1 is impaired. Furthermore, when the temperature of the liquid crystal is below −40° C., the liquid crystal layer 190 may even freeze, whereupon the LCD device 1 stops working.
Accordingly, what is needed is an LCD device that can circumvent the above-described difficulties.